This invention relates to projection systems and, in particular, to a mounting arrangement for a lens barrel onto a projector housing.
Projection systems use a lens or system of lenses to project an image from an image source onto a viewing scrcen. Light emitted by the image source or by another source separate from the image source is collected and projected onto the viewing screen. The light is concentrated into a projecting lens housed within a lens barrel mounted on the projector housing and projected onto the viewing screen. When viewing an image projected onto a screen it is sometimes necessary to manipulate the zoom lens to change the projected image from a larger image to a smaller image. Such zooming usually requires an adjustment to focus the image. Typically, this is done by rotating the projection lens barrel to move the lens elements back and forth within the lens barrel in a direction parallel to the optical axis. However, image projectors are often used for business meetings or other presentations that might often require changing the image size and it is inconvenient and/or time consuming to constantly re-focus the image.
In order to overcome the problem of having to re-focus the image after zooming some image projectors have a projection lens that has been compensated to allow a change in image size without having to re-focus the image. The compensation is done during the manufacture of the image projector by rotating the zoom lens to one extreme position in which the image is as large as it can get. The large image is then focused by rotating the projection lens barrel to move the lens elements internally. The zoom lens is then rotated to an extreme opposite position in which the image is as small as possible. The small image is then focused by moving the entire projection lens barrel either toward or away from the active element, such as, for example, a projection screen. The projection lens barrel is then locked in place and the lens compensation is complete.
Currently, image projectors with a compensated lens system employ various types of components to lock the projector lens barrel in place after compensation has been completed. For example, such projectors may include a projector lens barrel connected to the projector housing by screw threads with the lens barrel is locked in place by set screws. The set screws extend through threaded holes in the lens barrel and the projector housing. In order to compensate the projector lens the set screws must first be loosened and the projection lens barrel rotated about the screw threads in a direction substantially parallel to a focal axis to focus the image. After the lens has been compensated the projection lens barrel is then locked in place by tightening the set screws. Securing the lens barrel in place in this manner requires the user to hold the projection lens barrel in place while tightening the set screws. This can be awkward and may result in inadvertent movement of the projection lens barrel causing the lens to be less than optimally compensated. Furthermore, such systems require difficult manufacturing steps, such as, for example, machining small threaded holes for the set screws. Other image projectors may use other types of components such as, for example, shims to lock the projection lens in place after it has been compensated. However, the use of shims and other similar components are similarly awkward.
The present invention overcomes the above-described problems by providing a mounting for a projection lens barrel onto a projector housing that allows the user to more easily and accurately adjust and lock the projection lens barrel compensate the lenses. This is accomplished by mounting the projection lens barrel onto the projector housing with guide pins that cooperate with guide slots in the projector housing. The guide pins follow along the guide slots to advance or retract the projection lens barrel along an axis as the projection lens barrel is rotated to allow a more controlled and quick compensation operation. A spring actuated collet locks the projection lens barrel in place.
The projector housing generally includes a one-piece casting with an integrally formed projection lens barrel mounting portion. The barrel mounting portion includes guide pins that may be formed in a variety of shapes and configurations that are integral with the barrel mounting portion. Alternatively, the guide pins may formed separately and later press fit or otherwise secured to the barrel mounting portion. The projection lens barrel is formed with guide slots that cooperate with the guide pins so that the projection lens barrel can easily be rotated to advance and retract the projection lens barrel to focus a projected image. Once the projected image is focused the projection lens barrel is locked in place by a spring actuated collet.
The present invention eliminates the use of screw threads, set screws, shims and other similar components to lock the projection lens barrel in position.
It is an object of the invention to provide a mounting system for a projection lens barrel on an image projector housing that provides a more accurate and easy adjustment of the projection lens barrel to compensate the lens.
Another object of the present invention to provide quick and easy arrangement to lock the projection lens barrel in an adjusted position.
Still another object of the present invention is to provide a spring actuated collet to lock the projection lens barrel in the adjusted position.
A further object of the invention is to provide a projection lens barrel mounting system that eliminates screw thread connections, reduces the number of parts and is easier to manufacture.
Yet another object of the invention is to provide a projections lens barrel mounting system in which compensation of the projection lens is convenient and simple.
Additional objects and advantages of this invention will be apparent from the following detailed description of preferred embodiments thereof which proceeds with reference to the accompanying drawings.